diff --git a/ckan/src/ckanext-igsn-theme/ckanext/igsn_theme/sample_repository_schema.yaml b/ckan/src/ckanext-igsn-theme/ckanext/igsn_theme/sample_repository_schema.yaml
index 3657fc03..13adf4c7 100644
--- a/ckan/src/ckanext-igsn-theme/ckanext/igsn_theme/sample_repository_schema.yaml
+++ b/ckan/src/ckanext-igsn-theme/ckanext/igsn_theme/sample_repository_schema.yaml
@@ -239,6 +239,7 @@ dataset_fields:
   label: User Specified Keywords
   required: true
   preset: tag_string_autocomplete
+  validators: not_empty tag_string_convert
   help_text: Keywords help with the discovery of the physical sample
   groupBy: About Sample